Inertization methods for preventing and extinguishing fires in closed spaces are known in firefighting technology. The resulting extinguishing effect of these methods is based on the principle of oxygen displacement. As is generally known, normal ambient air consists of 21% oxygen by volume, 78% nitrogen by volume and 1% by volume of other gases. To extinguish or prevent fires, an inert gas of pure or 90% nitrogen is introduced, for example, to further increase the nitrogen concentration in the protected area at issue and thus lower the oxygen percentage. An extinguishing effect is known to occur when the percentage of oxygen falls below about 15% by volume. Depending on the inflammable materials contained within the respective protected area, further lowering of the oxygen percentage to, e.g., 12% by volume may additionally be necessary. Most inflammable materials can no longer burn at this oxygen concentration.
The oxygen-displacing gases used in this “inert gas extinguishing method” are usually produced by a device, or are stored compressed in steel canisters in specific adjacent areas. Inert gas mixtures of, for example, 90%, 95% or 99% nitrogen (or another inert gas) are used in this method. The steel canisters or the device to produce the oxygen-displacing gas constitutes the so-called primary source of the inert gas fire-extinguishing system. In case of need, the gas is then channeled from this source through a pipeline system and the corresponding outlet nozzles into the respective protected area. In order to keep the fire risk as low as possible should the primary source fail, secondary sources of inert gas are occasionally employed as well.
All the methods known to date for increasing the safety of such inert gas extinguishing fire prevention systems focus on preventing the flow of gas necessary to maintain an inertization concentration. Thus, there are an existing number of mechanisms which specify the different inert gas sources for the primary, as well as for any potentially provided and safety-increasing secondary inert gas sources. The secondary inert gas source will then kick in when the primary inert gas source fails.
However, a common shortcoming in all of these mechanisms and methods is that none have a safety mechanism in the event of an uncontrolled continuation of inert gas inflow, even when the inertization level has since reached a value which unfailingly prevents fires.
However, having an inert gas concentration which is too high can occur when an inadvertent equalization of the inertization gas concentration level occurs due to leakage between adjacent areas of differing inertization levels. A conceivable further shortcoming would be the failure of the control mechanism governing the supply of inert gas or the generator used to produce the inert gas, not turning off or the supply valve no longer having a tight seal and continuing to let inert gas flow into the protected area.
The reason for a high inertization level with yet an equivalently relatively high oxygen content can be rooted in the fact that either people are occupying the protected area or that it must be possible for people to enter the protected area even when an increased concentration of inertization gas is used to prevent fires. The continuous inflow of inertization gas into the protected area thus, not only results in higher costs for the continuous production of inert gas or the release of inert gas from primary and/or secondary sources, but it also affects particularly critical issues relative the safety of the people within the protected area.
Accordingly, based on the problems described above in safely engineering an inert gas fire extinguishing system, an inertization method which can reliably reduce inertization concentrations which are too high, or which are too high for specific requirements such as personnel entering the protected area, is needed.